'''
@Problem description:
You are given two non-empty linked lists representing two non-negative integers.
The digits are stored in reverse order and each of their nodes contain a single digit.
Add the two numbers and return it as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.
给两个存有非负整数的非空单链表，实现加法运算。

@For example:
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.
'''


# Definition for singly-linked list.
class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None

class AddTwoNumbersSolution:
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        dummyHead = ListNode(None)
        p, q, curr = l1, l2, dummyHead
        carry = 0
        while (p or q or carry):
            sum = getattr(p, 'val', 0) + getattr(q, 'val', 0) + carry
            carry = int(sum / 10)
            curr.next = ListNode(sum % 10)
            if p is not None:
                p = p.next
            if q is not None:
                q = q.next
            curr = curr.next
        return dummyHead.next
